Contrast enhancement for plant cell viewing

It’s difficult to see cells under a regular brightfield microscope when they don’t have pigment or stained with color.  The reason is that the light source of a brightfield microscope was placed directly underneath the specimen.  The light penetrate the specimen to illuminate the specimen and finally reach your retina.  There is very little deflection of the light to create the contrast.  Some simple filters can be added to the optical train to create the contrast.

Figure 1.  Onion epidermis cell under regular brightfield microscope.

 

Figure 2.  adding a darkfield filter to the light path, the cell wall can be easier to see.

Figure 3. Based on the darkfield technique,  The Rheinberg illumination, a form a optical staining, can stain the specimen without chemical stain.  The method used a color filter consists of two or more colors to allow the light with different color come from different direction which create the structure to be “Stained” with different color.  The above image was viewed under a Rheinberg filter with green center and red peripheral.

Figure 4. Of course, it is inevitable to use chemical staining if the structure of interest has very different chemical composition but very little in deflecting light.  The above picture is an onion epidermis cell with the nucleus in the center.  The specimen was stained with Methylene blue.  The nucleus was darker because methylene blue has stronger binding to nucleic acid than cytoplasm.

The steps for making the filters was described earlier at Laboratory and Home Science Resources.

Moth infested my Asian Pear

Couple moth ago I encounter serious problem of insect infestation of my Asian pear.  The secret is finally revealed.  The insect infested my Asian pear tree is the codling moth.  I catched several adult moths in my front yard.

More links about codling moth:
http://en.wikipedia.org/wiki/Codling_moth
http://crawford.tardigrade.net/bugs/BugofMonth33.html

Infestation of Asian Pear

Two years ago, my Asian pear trees (Niitaka and Hosui) were infected with fireblight.  They were almost die.  Couple applications of fertilome fireblight spray (21% Streptomycin) during budding and flowering seemed to take care of the problem this year.  Unfortunately, I wasn't pay much particular attention when the tree was starting to produce fruit.  I was just about to thin the fruits when they reach the nickel size.  I found some ugly tiny fruits.

The hosui pears were bubbled up to form a very strange shape.

Some were completely infested

Some fruits were producing white tubes and orange dust

Cut the fruit open and place in under my stereo microscope.
It appears that there are some sort of insect infestation in isde.

The white tube under stereo microscope.

I sent the pictures to Georgia Gardener.  I received the response. It appears that the white tubes are from some sort of fugal infection similar to Cedar - Hawthorn rust (The fungus develops on a cedar tree and then infects hawthorn trees growing close by. After growing on the leaves, orange, dusty spores are released that colonize nearby cedar trees.)  After research a little bit, the same type of rust fungus also form similar life-cycle between the juniper and pear/apple.  I also received the response from the Gwinnett county agriculture extension about the insect infestation.  They might be codling moth or Asian fruit moth.  I am not sure which one.  I am going to set up some trap to collect some moth during the summer.
It looks like I will have smaller crop this year.  The infection is serious. It almost wiped out three quarters of all my fruits.  I will remember to treat the tree when my tress start setting fruits next year.